The narrow-waisted Hymenoptera
Wasps and bees belong to the order Hymenoptera – one of the largest insect groups, which includes ants. Hymenoptera adults nearly all have a narrow waist, between the thorax and abdomen. They have two pairs of membranous wings, the front pair larger. Some are wingless.
Many species form colonies and have a social structure with specialised roles, but others live alone. In some species the female’s ovipositor (egg-laying tube) doubles as a stinger. Males do not sting.
Differences between wasps and bees
Wasps and bees are similar in most respects – bees are really a sub-group of wasps. Wasps have few or no hairs. Most wasp larvae feed on invertebrates, and adults mainly on sugary food such as nectar.
Bees have hairy bodies. They are totally vegetarian, and mostly feed their larvae on pollen.
The Hymenoptera life cycle has four stages:
- The adult female lays eggs.
- A larva (without legs) hatches, eats and grows.
- It forms a pupa.
- The adult eventually emerges.
Thousands of native species
New Zealand has an estimated 2,000–3,000 species of wasp and bee, most of which are native. The exact number is not known, as new species are still being found. Most are not very noticeable, and many are tiny. Groups include wood wasps and sawflies, parasitic wasps, stinging wasps, hunting wasps and bees.
Conspicuous introduced species
More easily seen are the introduced German and common wasps, paper wasps, honeybees and bumblebees. They form a tiny fraction of the total number of species, but they cross our paths more often.
Sawflies and wood wasps
The sawflies and wood wasps are a primitive group, separate from all the other Hymenoptera. Early in the evolution of wasps, this group stayed relatively unchanged, while the ancestors of most of today’s wasps developed a narrow waist and other features.
New Zealand has only three native species of primitive wasp, all hard to find. Little is known of their biology and diet, but most of this group feed only on plant tissue.
The best known is a parasite, Guiglia schauinslandi, which eats the larvae of wood-boring beetles and other wood wasps.
Introduced sawflies and wood wasps
Several accidentally introduced sawflies and wood wasps have become very common. Some, like the pear and cherry slug (actually the larval stage of Caliroa cerasi), and the eucalyptus blotch leaf miner (Phylacteophaga froggatti), are pests of cultivated plants. Larvae of the European sirex wood wasp (Sirex noctilio) feed in the wood of conifers, particularly radiata pine, and can cause considerable damage in plantation forests.
The most common primitive wasp is the willow sawfly (Pontania proxima). Its larvae feed inside willow leaves and make the leaf grow into a hard, reddish lump or gall, seen all over New Zealand.